In a high speed communication system, most of serial interfaces do not have any accompanying clock. As a result, in the communication system a receiver needs to recover the clock from a transmitter in order to sample the data on serial lines. To recover the sampling clock, the receiver needs a reference clock of approximately the same frequency. Further, to generate the recovered clock, the receiver needs to phase align the reference clock to the transitions on the incoming data stream. This process is called as clock recovery. Sampling of that incoming data signal with the recovered clock to generate a bit stream is called as data recovery. Together, the entire process is called Clock Data Recovery, or CDR. CDR is required to recover data from incoming data stream in the absence of any accompanying clock signal, without any bit errors due to over/under sampling.